This invention relates to a method of preparing a polyfluoroaldehyde or a polyfluoroacetal from a polyfluoroalkene. A representative of polyfluoroaldehydes that can be prepared by this method is 3,3,3-trifluoropropanal which is of use as the material of intermediates of some medicines and agricultural chemicals. 1,1-Dialkoxy-3,3,3-trifluoropropane is a representative of polyfluoroacetals which can be prepared by this method and can be converted into polyfluoroalkylcarboxylic acids useful as lubricants, surface treating agents and intermediates of some medicines and agricultural chemicals.
It is known that 3,3,3-trifluoropropanal CF.sub.3 CH.sub.2 CHO is obtained by oxidation of 3,3,3-trifluoropropanol CF.sub.3 CH.sub.2 CH.sub.2 OH with sodium dichromate (J. Am. Chem. Soc., 72, 3370(1950)) or by catalytic hydration of trifluoropropyne CF.sub.3 C.tbd.CH (J. Am. Chem. Soc., 74, 650(1952) ). However, neither of these methods is deemed industrially practicable because of difficulty in acquiring the starting material and insufficient yield of the desired aldehyde.
As to preparation of 1,1-dialkoxy-3,3,3-trifluoropropane CF.sub.3 CH.sub.2 CH(OR).sub.2, U.S. Pat. No. 2,883,429 shows reacting a corresponding trifluoroalkenyl ether with an alcohol in the presence of a base. However, the starting material of this method is very expensive and difficult to acquire as an industrial material since it has to be synthesized by complicated multi-stage reactions.